In order to provide services, wireless communication systems have to use a constant range of frequency bands. Because the frequency bands are rare resources, it cannot be guaranteed that a bandwidth of a desired size is provided anytime, anywhere. Further, the size of a required system bandwidth varies according to each country, according to a service provider's intention. However, the system standard does not define various system bandwidths enough to meet all the requirements of a system bandwidth. This is because predefining various system bandwidths is accompanied by many difficulties owing to the uncertainty of a required system bandwidth. Thus, there is a need for an alternative for, without an increase of system complexity and without a reduction of system transmission efficiency, flexibly supporting various system bandwidths required by service providers in addition to a basic definition of a system bandwidth.